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[DPRG] re: 32k memory and cache memory

Subject: [DPRG] re: 32k memory and cache memory
From: Robert L. Jordan rljordan at airmail.net
Date: Mon Oct 16 17:31:03 CDT 2000

Thanks for the good info from everyone on the list.
Regards,
Robert L. Jordan

-----Original Message-----
>From:	Peter Welty [SMTP:pwelty at utilx.com]
Sent:	Monday, October 16, 2000 4:08 PM
To:	'Robert L. Jordan'
Subject:	RE: [DPRG] re: 32k memory and cache memory

QFP = Quad Flat Package
SOIC = Small Outline Integrated Circuit

Some data sheets dont contain the information about the size of the package,
they just specify "SOIC" and assume that you can find the information
somewhere. Basically, the SOIC is like the DIP package but with the pins set
up for surface mounting. (They are a little smaller, but usually the
pin-outs match.)

The QFP is a little different, it uses all four edges of the package (hence,
quad) and is usually square.  There are many types of other "Surface Mount"
packages out there, Maxim makes one that I come across all the time called a
"microMAX" that is smaller than an SO8. 

-----Original Message-----
>From: Robert L. Jordan [mailto:rljordan at airmail.net]
Sent: Monday, October 16, 2000 1:22 PM
To: 'dean.hall at computer.org'; dprglist at dprg.org
Subject: RE: [DPRG] re: 32k memory and cache memory


Dean,

What are the surface mount packages QFP, SOIC?
I recognize BGA as Ball Grid Array. These have lots of gold dots under the
package.

What is QFP and SOIC?

Thanks,
Robert L. Jordan


-----Original Message-----
>From:	Dean Hall [SMTP:dwhall256 at yahoo.com]
Sent:	Monday, October 16, 2000 1:12 PM
To:	dprglist at dprg.org
Subject:	[DPRG] re: 32k memory and cache memory

Kip wrote:
> Does anyone know any other manufacturers that are 
> still in production with a 32K x 8 70 ns SRAM in a
> DIP package? (And their part numbers?)

Hobbyists will start seeing this more and more.  All
chips are going surface mount.  It's becoming cost
effective to eliminate the DIP package.  (I just hope
that QFP and SOIC stay around and don't lose out to
BGA.  I can solder the 0.05" QFP and SOIC, BGA is a
trifle tricky to get the old soldering pin under there
<smiley>).

I don't have knowledge of who is still producing DIP
SRAMs, but I know who still supplies them: All
Electronics.


Hamid wrote:
> Recently I'm thinking about using cache SDRAMs on
old
> 386 and 486 main boards. Most main boards have 8 of
> them in 28 pin, 0.3" DIP form.  They are space
saving 
> and cost almost nothing. They are very fast too,
> usually 10-20 ns, thus I expect them to be suitable 
> for any hobby application.
> Anyone else has used them before? any ideas?

The reason most boards have 8,16, or 32 of them is
because each individual chip has only a fraction of
the data bus width (1,2, or 4 bits wide).  This means
you would have to put at least 8, 4, or 2 of the chips
in your design.  Not too difficult, just consumes
board space.  

PS: using a 10ns SRAM versus a 70ns SRAM will make no
difference with most micros.  If they both meet the
timing spec, they'll present the data on-time; but
they won't make the micro's bus cycle any faster.
(just like catching a city bus: it doesn't matter if
you run to the stop or walk there, as long as you're
there by the time the bus leaves.)

!!Dean

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